Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Montreal, Quebec, Canada.
Spine (Phila Pa 1976). 2012 Jun 15;37(14):E823-35. doi: 10.1097/BRS.0b013e31824b7154.
Numerical modeling and simulations of scoliotic spine instrumentation using monoaxial, uniaxial, polyaxial, and multiple-degrees-of-freedom (6DOF) postloading pedicle screws.
To biomechanically analyze the general curve reduction effects and bone-screw force levels of monoaxial, uniaxial, polyaxial, and 6DOF pedicle screws for scoliotic spine instrumentation.
The ideal spinal fusion construct for treating scoliosis is still debatable. Studies on the effects of different types of implants were mainly based on postoperative radiograph measurements. Systematic studies are yet to be done on how bone-screw forces are correlated with screw types.
Computer biomechanical models were built using 3-dimensional geometry and spine stiffness of 10 patients with adolescent idiopathic scoliosis having undergone spinal instrumentation. The surgical instrumentations were simulated each time, using a different type of screw. For each case and screw type, 15 screw placement variations were simulated to investigate their effects on bone-screw forces.
The maximum differences between different screw types were 6.4°, 1.1°, and 4.7°, respectively, for main thoracic Cobb angles, main thoracic apical vertebral rotation, and thoracic kyphosis (1.2°, 0.3°, and 0.3° on average). The average bone-screw forces were higher for monoaxial (229 N ± 140 N) than uniaxial (206 N ± 122 N), polyaxial (141 N ± 99 N), and 6DOF screws (103 N ± 42 N). Bone-screw forces with monoaxial screws were, respectively, 1.1, 2.5, and 25 times more sensitive to screw placement variation than uniaxial, polyaxial, and 6DOF screws.
The bone-screw loads of different screws were significantly different. The descending order of bone-screw loads was monoaxial, uniaxial, polyaxial, and 6DOF screws. For patients with large and stiff spinal deformities or for patients with compromised bone quality, screws with more degrees of freedom offer better perspective to reduce bone-screw connection failure.
使用单轴、单轴、多轴和多自由度（6DOF）后加载椎弓根螺钉对脊柱侧凸脊柱器械进行数值建模和模拟。
生物力学分析单轴、单轴、多轴和 6DOF 椎弓根螺钉对脊柱侧凸器械的总体曲线减少效果和骨螺钉力水平。
治疗脊柱侧凸的理想脊柱融合结构仍存在争议。关于不同类型植入物影响的研究主要基于术后 X 光片测量。关于骨螺钉力与螺钉类型的相关性，尚未进行系统研究。
使用 10 例青少年特发性脊柱侧凸患者的三维几何形状和脊柱刚度建立计算机生物力学模型，这些患者接受了脊柱器械治疗。每次模拟手术器械时，使用不同类型的螺钉。对于每个病例和螺钉类型，模拟了 15 种螺钉放置变化，以研究它们对骨螺钉力的影响。
不同螺钉类型之间的最大差异分别为胸椎 Cobb 角、胸椎顶椎旋转和胸椎后凸（平均分别为 6.4°、1.1°和 4.7°）。单轴螺钉（229 N±140 N）的平均骨螺钉力高于单轴螺钉（206 N±122 N）、多轴螺钉（141 N±99 N）和 6DOF 螺钉（103 N±42 N）。单轴螺钉的骨螺钉力分别比单轴、多轴和 6DOF 螺钉对螺钉放置变化的敏感性高 1.1、2.5 和 25 倍。
不同螺钉的骨螺钉负荷有显著差异。骨螺钉负荷的降序为单轴、单轴、多轴和 6DOF 螺钉。对于具有大而僵硬的脊柱畸形或具有受损骨质量的患者，具有更多自由度的螺钉提供了更好的降低骨螺钉连接失败的前景。
